App as Windows XP shell

So I want to have my SDL app be the first and only application that runs when
Windows XP boots.

I figured out how to get the application to launch instead of explorer as the
shell, but when other programs are launched from my app they appear below it.
It seems if an application is the shell, it sits above everything else.

Is there some way to change this?

Also I can’t make the SDL_FULLSCREEN work when it’s a shell.
It always starts in windowed mode.

Everything works fine and dandy when the application is just run (not as the
shell).

Any suggestions?
Anyone know a better way to make my app the only one available when windows
launches?>From my app the user can select and launch other applications.